Measurement And Calculation Of Wide Frequency Two-port Network Parameters Of The110kV Transformer

Wide frequency network characteristics of the transformer is needed to studyelectromagnetic transient model considering the affect of very fast transient overvoltage(VFTO) and lightning overvoltages. It is also the basis of the winding state detectionbased on frequency response analysis (FRA).Based on the National Natural Science Foundation project, Research of theEstablishment of the Passive Wide Band Macro-model of Transformer Device(No.50977301), the calculation method of Multi-conductor transmission line model andapplication of the finite element method are studied.Firstly, an Agilent4395A network analyzer is used to measure two transformers,which types are D9-10/10and SS11-20000/110. Because the110kV transformer hasthree phases, the influence of other phases and their grounding mode is analysed.Secondly, the calculation method for wide frequency admittance parameters isproposed based on the multi-conductor transmission lines model, combined with finiteelement method. The method impoves the previous calculation formula based on matrixtransformation. At the same time, it deduces the whole calculation process of thedouble-winding admittance parameters on decoupling of transmission line model bymode current and voltage, which also applies to one or more windings easily. Also, itavoids the complex numerical equation calculation of the previous calculation method, aswell as improves the computational efficiency.Thirdly, the sparse matrix method is proposed to solve the problem of too largematrix order number. Considering the effect of several adjacent coils only, the matrixcharacteristics of Y and Z is analyzed, based on which the block storage and computationmethod is applied. And frequency-domain model is solved based on sparse matrixoperation. The method is applied to the D9-10/10transformer and the consistency of Themeasured results and the calculated results verifies the feasibility of method.Lastly, the specific calculation process of the transformer, which type isSS11-20000/110, is presented, based on the structure of the transformer, the windingsconnections and so on. After the calculation, the correctness of this method has beenverified by comparing the calculation results of the transformer with the measurementresults.